A suspension device for a rear wheel of a motorcycle or a steering ski of a snowmobile comprises a suspension spring that absorbs an impact from a road surface and a shock absorber that attenuates expansion and contraction of the suspension spring.
JP08-270713A, published by the Japan Patent Office in 1996, proposes an adjuster for adjusting a damping force generated by this type of shock absorber during contraction.
The adjuster increases or reduces the damping force generated by the shock absorber during contraction by varying a flow area of a bypass passage through which working oil flows from an oil chamber that contracts in accordance with the contraction operation of the shock absorber to a reservoir tank provided on an outer side of the shock absorber.
The adjuster comprises a rotary member that is caused to perform a rotation operation, and a detent mechanism that positions and holds the rotary member in a predetermined rotary angle position.
The detent mechanism comprises a ball that is biased by a spring to project in a radial direction from the rotary member, and a plurality of ball latching grooves formed at predetermined angular intervals in a wall surface of a housing surrounding the rotary member in order to receive the ball.
When the adjuster is inoperative, the ball engages with one of the ball latching grooves to prevent the rotary member from rotating unintentionally. When the rotary member is operated to rotate using a jig or the like, the ball retreats to an inner side of the rotary member against the spring such that the rotary member rotates. As the rotation operation of the rotary member continues, the ball engages with the ball latching grooves in sequence every time the rotary member rotates by a fixed angle.
The rotary member can be operated to rotate in intervals of the fixed angle in accordance with variation in an operation feeling generated as the ball engages with and separates from the ball latching grooves, and by stopping the rotation operation in an engagement position between the ball and an arbitrary ball latching groove, the rotary member is held by the detent mechanism in the rotary angle position reached when the rotation operation was stopped until the rotation operation is resumed.